Unit 2: Air Part 1: Atmosphere

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Unit 2 AirPart 1 Atmosphere Climate

• Thank God men cannot fly, and lay waste the sky
  as well as the earth.  - Henry David Thoreau

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KEY IDEAS

• Earth is characterized by patterns of
  temperatures and precipitation.
• These patterns arise from the circulation of air
  and ocean water, which is ultimately driven by
  unequal heating of Earth by the Sun, the rotation
  of Earth, and Earths geographic features.
• Geographic variations in temperature and
  precipitation have led to the development of
  distinct terrestrial biomes, which are defines by
  their unique plant communities, and distinct
  aquatic biomes.

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ATMOSPHERE AND CLIMATE

• Weather - A description of short-term physical
  conditions of the atmosphere in a local area.
• An afternoon thunderstorm
• Climate - A description of the long-term weather
  pattern in a particular area.
• Temperature
• Humidity
• Wind
• Rainfall

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HOW DOES CLIMATE WEATHER AFFECT LIFE?

• Regional differences in temperature and
  precipitation collectively help determine which
  organisms can survive in each region.
• To understand these differences, we need to
  understand the processes that effect the
  distribution of heat and precipitation.
• These processes include
• Unequal heating of Earth by the Sun
• Atmospheric Convection Currents
• Rotation and Revolution of Earth on Tilted Axis
• Ocean Currents

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The Atmosphere

• The atmosphere is a layer of gasses surrounding
  the Earth consisting of 5 layers
• If the Earth were the size of an apple, the
  atmosphere would be the skin.

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Layers of the Atmosphere
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Layers of the Atmosphere

• Troposphere (0 km to 16 km 10 miles)
• Largest and lowest part of atmosphere.
• Weather occurs in this layer.
• Carbon dioxide is trapped in this layer, forming
  the basis of the greenhouse effect and global
  warming.
• Most dense layer Most of the gas (Nitrogen,
  Oxygen, Water Vapor) found here.
• Large amount of circulation and mixing
• Temperature decreases as altitude increases.

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Layers of the Atmosphere

• Stratosphere (16-50km 10-31 miles)
• Very stable, calm layer of the atmosphere Less
  dense due to distance from Earths gravitational
  pull.
• Used by aircraft.
• Contains the ozone layer (Made of Ozone
  molecules) Incoming UV rays reach higher
  altitudes first, thus the higher altitudes are
  warmer. (Temp increases as altitude increases)

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A Word about Ozone (O3)

• Ozone is a pale blue gas composed of 3 oxygen
  molecules.
• The layer of ozone absorbs MOST of the Suns
  ultraviolet-B (UV-B) radiation and ALL of its
  ultraviolet-C (UV-C) radiation.
• UV radiation can cause DNA damage and cancer in
  organisms, so the ozone layer provides a critical
  shield of protection for life on Earth.

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Layers of the Atmosphere

• MESOSPHERE (60-100 km)
• THERMOSPHERE (100 km-600 km)
• Blocks harmful X-ray UV radiation
• Contains charged gas molecules that, when hit by
  solar energy, begin to glow and produce light
• The interaction is driven by magnetic forces at
  the poles.
• EXOSPHERE
• Due to weaker gravitational pull on molecules at
  these altitudes, the pressure and density in each
  of these layers decrease as it extends into
  space.

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• Aurora Borealis (Northern Lights)

• Aurora Australis (Southern Lights)

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THE EARTH THE SUN

• The Sun has the greatest influence on Earth
• Affects its movement
• Determines day-night and seasonal cycles
• Driving climatic systems and long term climate
  cycles
• Provides energy for most life on Earth
• Also plays part in TIDAL movement by modifying
  the effect of the Moon to produce monthly
  variation in the tidal range.

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The Sun

• The Sun emits various types of radiation, most of
  which is absorbed by the ATMOSPHERE.
• The radiation that reaches the surface
• Visible Light Critical to producers
• Infrared Radiation
• Ultraviolet
• Intensity of solar radiation is not uniform
  around the Earth, thus.

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The Earth The Sun

• ..THE UNEVEN HEATING EFFECT, TOGETHER WITH THE
  EARTHS ROTATION, PRODUCE THE GLOBAL PATTERNS OF
  WIND AND OCEAN CIRCULATION THAT PROFOUNDLY
  INFLUENCE THE EARTHS CLIMATE!!

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THE EARTH THE SUN

• SOLAR YEAR Earth takes 365.25 days to orbit
  around the Sun (Revolve)
• EARTH DAY Earth spins (Rotation) on its axis
  once every 23 hours 56 minutes 4.09 seconds)
• Earth does not spin upright it has a 23.5 degree
  tilt. The tilt ALWAYS faces the SAME way Results
  in seasonal changes in sunlight and weather.

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Sun Angle Controls Sunlight Intensity

• At low angles (Oblique), sunlight spreads over
  much larger areas thus heats less effectively.
• At low angles, sunlight reflects from water ice
  more efficiently.

Garrison, 2005
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Poleward Heat Transport to Balance Unequal
Heating

• Equator would be hotter poles
  would be much colder without this transport.
• Transport by winds ocean currents.

Garrison, 2005
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Solar Radiation

• Visible light is energy waves that we can see as
  color.
• These pass through the atmosphere.
• Ultraviolet light is energy waves that we cannot
  see but can cause sun burns and cancer.
• These are absorbed by ozone in the stratosphere.
• Infrared radiation is the energy of the sun that
  we feel as heat.
• This is absorbed by carbon dioxide and water in
  the troposphere.

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Energy and the Greenhouse Effect

• Solar Radiation
• Of solar energy reaching outer atmosphere
• 25 reflected
• 25 absorbed
• 50 reaches earths surface
• Of the solar energy that reaches the surface,
  much is reflected
• Fresh clean snow 90
• Dark soil 3
• Net average of earth 30

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EARTHS TILT THE SEASONS

• Because of the 23.5 degree tilt of Earth on its
  axis, most regions of the world experience
  seasonal changes in temperature and
  precipitation.
• When the Northern Hemisphere is tilted toward the
  Sun, the Southern Hemisphere is tilted away from
  the Sun.
• The Suns rays strike the equator directly 2x a
  year the March equinox and the September
  equinox.
• On these days, virtually all regions experience
  12 hours of daylight and 12 hours of darkness.
• For the 6 months between March and September
  equinoxes, the N.H. tilts toward the Sun (more
  daylight hours than darkness)

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EARTHS TILT THE SEASONS

• On June 20 or 21 (June Solstice), the Sun is
  directly above the Tropic of Cancer (23.5 degrees
  N), the N.H. experiences more daylight hours than
  on any other day of the year.
• For the 6 months between September and March, the
  N.H. tilts away from the Sun and experiences
  fewer hours of daylight than darkness.
• On December 21 or 22 (December Solstice), the Sun
  is directly over the Tropic of Capricorn (23.5
  degrees South).
• On this day, the N.H. experiences its shortest
  daylight period of the year.

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EARTHS TILT THE SEASONS

• In summary, Earths tilt on its axis produces
  predictable seasons.

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Solar Radiation
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KEY CONCEPT

• UNEQUAL HEATING OF THE EARTH
• Caused by
• Variation in the angel at which Suns rays strike
  Earth
• -The tropics (near equator) hit at perpendicular
  angle.
• -Mid-latitude and polar regions are hit at more
  oblique angles.
• As a result, the Suns rays travel a shorter
  distance through the atmosphere to reach Earths
  surface in the tropics.
• In other words, at high latitudes, sunlight must
  pass through more atmosphere, and thus lose more
  of its energy.

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KEY CONCEPT

• UNEQUAL HEATING OF EARTH
• Caused by
• 2. Variation of amount of SURFACE AREA over
  which the Suns rays are distributed.
• -The perpendicular angle of rays in the tropics
  cause solar energy to be distributed over a
  smaller surface area there than at higher
  latitudes.
• - Shine light on ballyou get a focused orb of
  light.
• -Shine light on top of ball at oblique
  angel..you get an oval pool of dimmer light over
  a larger area.

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KEY CONCEPT

• UNEQUAL HEATING OF EARTH
• Caused by
• 3. Certain areas of Earth reflect more solar
  energy than others
• The percentage of incoming sunlight that is
  reflected from a surface is called its ALBEDO
• -The higher the albedo of a surface, the more
  solar energy it reflects, and the less it
  absorbs.
• -A white surface has a higher albedo than a
  black surface, so it tends to stay cooler.

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How Uneven Heating Drives Circulation

• The amount of heat in the atmosphere directly
  affects the movement of water.
• Warm air containing evaporated water rises higher
  into the atmosphere.
• Warm air is less dense than cool air.
• As warm air rises, heat is released into the
  atmosphere and the water vapor condenses.
• The condensed water then falls as rain or snow.

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PROPERTIES OF AIR

• 4 Properties of Air Determine How it Moves
• Density
• Vapor Capacity
• Adiabatic Heating or Cooling
• Latent Heat Release

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1. DENSITY OF AIR 2. VAPOR CAPACITY

• Less dense air RISES, dense air SINKS
• Warm air has a lower density than cold air
• Therefore, warm air rises
• Also, hot summer dayshigh humidity
• The warm air contains a lot of water
• Saturation Point Max. amount of water that can
  be in the air at a given temperature.
• When air temp. falls, its saturation point
  decreases water vapor condenses into liquid
  water, clouds form, and precipitation occurs.

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3. ADIABATIC HEATING COOLING

• As air rises higher in the atmosphere, the
  pressure on it decreases.
• The lower pressure allows the rising air to
  expand in volume, and this expansion lowers the
  temperature of the air
• Called ADIABATIC COOLING
• When air sinks towards the Earth, the pressure on
  it increases. The higher pressure forces the air
  to decrease in volume, and this decrease raises
  the temperature of the air
• Called ADIABATIC HEATING

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4. LATENT HEAT RELEASE

• The production of heat when water vapor
  condenses from a gas to a liquid.
• When water vapor in the atmosphere condenses into
  liquid form, energy is released (LATENT HEAT
  RELEASE)
• Explains how whenever water vapor in the
  atmosphere condenses, the air will become warmer
  and this warm air will rise.

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Convection Currents
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Atmospheric Convection Currents

• A.C.C. Global patterns of air movement initiated
  by unequal heating of Earth.
• Hadley Cells The convection currents that cycle
  between the equator and 30 degrees N and S.
• Solar energy warms humid air in the tropics. This
  warm air rises and eventually cools below its
  saturation point.
• The vapor condenses into clouds and
  precipitation. The now dry air sinks to Earths
  surface at 30 degrees N and S.
• As the air descends, it is warmed by adiabatic
  heating. This descent of hot, dry air causes
  desert environments to develop at those latitudes.

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HADLEY CELLS
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INTERTROPICAL CONVERGENCE ZONE

• Intertropical Convergence Zone (ITCZ)
• The area of Earth that receives the most intense
  sunlight, where the ascending branches of the 2
  Hadley cells converge.
• It is amplified by dense clouds and intense
  thunderstorm activity.

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POLAR CELLS

• Similar to Hadley Cells, the Polar Cells are
  convection currents that are formed by air that
  rises at 60 degrees N and S and sinks at the
  poles (90 degrees N and S).
• Between Hadley Cells Polar Cells lies a 3rd
  area of circulation, Ferrell Cells.
• Not convection cells movement driven by
  circulation of neighboring cells.

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GLOBAL AIR CIRCULATION
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RESULTS OF GLOBAL AIR CIRCULATION

• Distributes warm air away from the tropics and
  cold air away form the poles
• Allows for a wide range of warm and cold air
  currents to circulate between 30 and 60 degrees.
• Collectively, these convection currents slowly
  move the warm air of the tropics toward the
  mid-latitude and polar regions. This pattern of
  air circulation is largely responsible for the
  locations of rainforests, deserts, and grasslands
  on Earth.

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Earths Rotation Coriolis Effect

• Rotation of Earth has important climatic
  influence, particularly on the Prevailing Winds.
• As Earth rotates, its surface moves much faster
  at the equator than at other regions.
• Imagine standing still at the equator as Earth
  rotates
• Given that a single rotation is 24 hours, you
  would be traveling at much faster speed at the
  equator than at the poles.
• The faster rotation speeds at the equator cause a
  deflection of objects that are moving directly
  north or south.
• The deflection of an objects path due to Earths
  rotation is called the CORIOLIS EFFECT

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CORIOLIS EFFECT

• Massachusetts Institute of Tech (MIT)
• http//mit.tv/z79Q8o
• The prevailing wind systems of the world are
  produced by a combination of atmospheric
  convection currents and the Coriolis Effect
• If Earth did not rotate, the air within each
  convection cell would simply move directly North
  or South and cycle back again.

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Summary

• Simply stated, the atmospheric convection
  currents of tropical and polar latitudes, the
  mixing of air currents in the mid-latitudes, and
  the Coriolis effect cause the prevailing wind
  patterns that occur worldwide, although local
  features, such as mountain ranges, can alter wind
  directions.

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OCEAN CURRENTS

• Ocean currents are driven by a combo of
  temperature, gravity, prevailing winds, the
  Coriolis Effect, and the locations of continents.
  

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Ocean Currents

• As we have seen, the tropics receive the most
  direct sunlight throughout the year, and tropical
  waters are thus generally warm.
• Warm water, like warm air, expands and rises.
• This process raises the tropical water surface
  about 8cm higher in elevation than mid-latitude
  waters.
• This slight slope is enough for the force of
  gravity to make water flow away from the equator.

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Ocean Currents GYRES

• Large-scale patterns of water circulation that
  redistribute heat in the ocean
• Cold water from polar regions moves along the
  west coasts of continents, and the transport of
  cool air from above these waters causes cooler
  temperatures on land.
• Global prevailing wind patterns play a major role
  in determining the direction in which ocean
  surface water moves away from the equator.
• In the N.H., the trade winds near the equator
  push water from the northeast to the southwest
  and the Coriolis effect deflects this wind-driven
  current so that water actually moves from east to
  west.
• The overall effect Ocean SURFACE currents rotate
  in a clockwise direction in the N.H. in a CCW
  direction in the S.H.

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Ocean Currents UPWELLING

• These explain why some regions of ocean support
  highly productive ecosystems.
• Along west coasts of most continents, the surface
  currents diverge and cause deeper waters to rise
  and replace the water that has moved away. This
  upward movement of water to the surface is called
  Upwelling.
• The deep waters bring with them nutrients from
  the ocean bottom that support large populations
  of producers, which support large populations of
  fish.

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Ocean Currents THERMOHALINES

• Thermohaline Circulation Drives the mixing of
  surface water and deep water.
• Crucial to moving heat and nutrients around the
  globe.
• Driven by surface water that contain unusually
  large amounts of salt.
• 1. Warm water flows from Gulf of Mexico to the
  North Atlantic where some of it freezes and
  evaporates
• 2. The remaining water, now saltier and denser,
  sinks to the ocean bottom
• 3. The cold water travels along the ocean floor,
  connecting the worlds oceans.
• 4. The cold, deep water eventually rises to the
  surface and circulates back to the North Atlantic.

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Ocean Currents HEAT TRANSPORT

• Ocean currents can affect the temperature of
  nearby landmasses.
• Ex The ocean current known as the Gulf Stream
  originates in the tropics near the Gulf of Mexico
  and flows NE across the Atlantic toward Europe.
  As it moves warm waters north, the stream brings
  large amounts of heat energy to cooler regions,
  moderating temps in latitudes that otherwise
  would be much colder.

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Concern

• One major concern about global warming is that
  increase air temperatures could accelerate the
  melting of glaciers, which could make the waters
  of the North Atlantic less salty and thus less
  likely to sink.
• Such a change could potentially shut down
  thermohaline circulation and stop the transport
  of warm water to Western Europe, making it a much
  colder place.

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ALMOST DONE!!
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El Nino-Southern Oscillation

• Earths atmosphere and ocean interact in complex
  ways.
• Periodically (every 3 to 7 years), these
  interactions cause surface currents in the
  tropical Pacific Ocean to reverse direction.
• First, the trade winds near South America weaken,
  allowing warm equatorial water from the western
  Pacific to move eastward toward the west coast of
  South America.
• The movement of warm water and air toward South
  America suppresses upwelling off the coast of
  Peru and decreases productivity there, reducing
  fish populations near the coast.

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El Nino-Southern Oscillation

• This phenomenon is called El Nino (the baby
  boy) because it often begins around the December
  25 Christmas holiday.
• El Nino can last from a few weeks to a few years.
  These periodic changes in wind and ocean currents
  are collectively called the El Nino-Southern
  Oscillation (ENSO)
• Globally, the impact of ENSO includes cooler and
  wetter conditions in the southeastern US and
  unusually dry weather in southern Africa and
  Southeast Asia.

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Rain Shadows

• Air moving inland from the ocean often contains a
  large amount of water vapor.
• This air meets the windward side of a mountain
  range (the side facing the wind), it rises and
  begins to experience adiabatic cooling.
• Because water vapor condenses as air cools,
  clouds form and precipitation falls.
• As is the case with Hadley cells, this
  condensation causes latent heat release, which
  helps to accelerate the upward movement of the
  air. Thus, the presence of the mountain range
  causes large amounts of precipitation to fall on
  its windward side. The cold, dry air then travels
  to the other side of the mountain range (leeward
  side), where it descends and experiences higher
  pressures, which cause adiabatic heating.

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RAIN SHADOWS

• This now warm, dry air produces arid conditions
  on the leeward side of the range forming a region
  called a RAIN SHADOW.
• It is common to see lush vegetation on the
  windward side of a mountain range and very dry
  conditions on the leeward side.